Diallyl trisulfide exerts anti-inflammatory effects in lipopolysaccharide-stimulated RAW 264.7 macrophages by suppressing the Toll-like receptor 4/nuclear factor-kappa B pathway

Abstract

Diallyl trisulfide (DATS; di-2-propen-1-yl trisulfide) is an organic polysulfide compound found in garlic and other allium vegetables. Although certain studies have demonstrated that DATS possesses strong anti-inflammatory activity, the underlying molecular mechanisms remain largely unresolved. In the present study, the anti-inflammatory potential of DATS was investigated using the murine macrophage RAW 264.7 cell model. At non-toxic concentrations, DATS inhibited the production of nitric oxide (NO) and prostaglandin E, by inhibiting inducible NO synthase and cyclooxygenase-2 expression at the transcriptional level in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. DATS attenuated the release of the pro-inflammatory cytokines, tumor necrosis factor-a and interleukin-1 beta, by inhibiting mRNA expression, respectively. DATS also suppressed LPS-induced DNA-binding activity of nuclear factor-kappa B (NF-kappa B), as well as the nuclear translocation of the NF-kappa B p65, which correlated with the inhibitory effects of DATS on inhibitor kappa B (I kappa B) degradation. In addition, DATS was observed to significantly suppress LPS-induced Toll-like receptor 4 (TLR4) and myeloid differentiation factor 88 expression and the binding of LPS to macrophages, indicating the antagonistic effect of DATS against TLR4. Furthermore, blocking TLR4 signaling with the specific TLR4 signaling inhibitor, CLI-095, increased the anti-inflammatory potential of DATS in LPS-stimulated RAW 264.7 macrophages. These data demonstrate that DATS may attenuate the initiation of LPS-mediated intracellular signaling cascades by suppressing activation of NF-kappa B and by inhibiting binding of LPS to TLR4 on macrophages.